Since the prediction by Strominger, Amer. J. Med., 39, 708 (1965), that 6-methylpenicillins and 7-methylcephalosporins should have an enhanced antimicrobial activity; and the recent discovery of the naturally occurring 7-methoxycephalosporins, R. Nagarajan, et al., J. Amer. Chem. Soc., 93, 2308 (1971), considerable interest has developed in the synthesis of .beta.-lactam antibiotics bearing a substituent in the position .alpha. to the .beta.-lactam carbonyl of the penicillin and cephalosporin antibiotics.
In copending application Ser. No. 268,358, filed July 3, 1972, now abandoned, the preparation of 6-acylamido-6-lower alkylthiopenicillanic acids, 7-acylamido-7-lower alkylthiocephalosporanic acids and 7-acylamido-7-lower alkylthiodeacetoxycephalosporanic acids is described. The present invention relates to a process for converting the thio substituted penicillins and cephalosporins described therein to 6-alkoxy substituted penicillins and 7-alkoxy substituted cephalosporins.